Liquid crystals play an important part in the procession of advanced technology. They are unparalleled in their properties and are widely exploited for technical innovations including LCD displays for monitors, portable computers, cell phones, digital clocks and other electrical appliances.
Visual picture of phase transitions
The liquid crystal state is a distinct phase observed between the crystalline (solid) and isotropic (liquid) states.
Several different transition phases occur with liquid crystals which include the Nematic, Smectic and Cholesteric phases.
Differential scanning calorimetry (DSC) is an excellent instrument for investigating the stage transitions of liquid crystals. It can rapidly and easily beat the temperatures at which melting and phase transitions occur.
Hot-stage polarization microscopy is an innovative technique that is widely exploited for the visual picture of phase transitions. This technique allows the user to directly observe morphological changes in a taste as it is heated or cooled. Changes in the shape, structure and colour of crystals can be observed along with their size and number. This is very valuable information within research and growth and tone control.
Achieving excellent results with the good combination
The next example shows how cholesteryl myristate can be easily investigated and characterized using the METTLER TOLEDO DSC 1 combined with the FP82 hot-stage microscopy system.
The DSC curve in Figure 1 illustrates the phase behavior of cholesteryl myristate. Three liquid-liquid transitions can be discovered upon heating. If the taste is now observed under polarized light so the individual transitions can be identified.
When the FP82 hot-stage microscopy system is exploited in compounding with the DSC 1 it is potential to directly detect and describe the individual phase transitions which agree to each DSC peak. Figure 2 shows that the taste has changed from the solvent-crystallized form to the smectic phase at 75.5 C. Figure 3 shows that at 79.1 C the crystals have changed to the cholesteric phase and show a structureless gray image.
The DSC 1 combined with the FP82 hotstage microscopy system is a potent instrument for identifying and characterizing liquid crystal phase transitions. The FP82 hotstage microscopy system yields a wealth of data that is complemental to the information obtained from the DSC 1. Furthermore, polarization microscopy and DSC measurements provide a perfect thermal image of each sample.
No comments:
Post a Comment